LONDON – Royal Bank of Scotland Group Plc is in talks to sell its minority stake in credit-card processor WorldPay Ltd. to its private-equity co-owners, according to two people with knowledge of the matter.

Britain’s largest publicly owned lender is negotiating with Advent International Corp. and Bain Capital LLC to sell its remaining holding of about 20 percent in the Cambridge, England-based company for 250 million pounds ($402 million) within the next month, said the people, who asked not to be identified because the talks are private.

RBS sold a majority stake in WorldPay to the two Boston-based private-equity firms in a deal valued at 1.9 billion pounds, including a 1.2 billion-pound debt package, in 2010. In March, WorldPay’s owners increased the company’s debt, paying themselves a 340 million-pound dividend and repaying lower- ranking debt holders.

WorldPay generated 305 million pounds of earnings before interest, taxes, depreciation and amortization in 2012.

In a statement on Nov. 1, following Chancellor of the Exchequer George Osborne’s decision to have RBS transfer $61 billion of its worst loans to an internal bad bank, RBS said it will also speed up plans to sell its stake in Providence-based Citizens Financial Group Inc. to bolster capital.

The lender will sell an initial stake in the second half of 2014 and sell the rest by the end of 2016. The original plan, outlined in February, had been to start an initial public offering in two years.

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